In electrical-discharge machining of this type, the wire or like elongated electrode, which will hereinafter be referred to as "wire electrode", is held under tension and displaced to travel through a machining zone flushed with a machining liquid which is usually distilled water and a series of electric pulses are applied across the machining gap between the wire electrode and the workpiece to effect time-spaced electrical-discharges between them to remove material from the workpiece.
The transverse displacement of the workpiece relative to the travelling-wire electrode to follow the material removal is usually effected automatically by a control system under programmed instructions which define a predetermined cutting path.
I have now found that in order to achieve better machining accuracy and efficiency and stability of operation, compensation for the machining zone or workpiece thickness is essential.
In prior practice, the wire electrode has been passed through the machining zone at a constant speed and machining pulses of a constant pulse duration, interval and peak current have been utilized throughout a given machining operation. As a consequence, with change in the thickness of the workpiece, a change is brought about in the amount of the wire electrode wear, this local wear variation limiting the machining accuracy attainable and rendering the operation unstable. It can also be a cause of the rupture of the wire electrode.